The present invention relates to gas separation and more particularly to a dirty gas inlet configuration for cyclone-type particulate matter gas separation devices.
Cyclone-type separators are typically comprised of a generally cylindrical housing with a dirty gas inlet at one end having means for imparting a rotating or whirling motion to the incoming dirty gas stream to centrifuge particulates therefrom, means to direct the flow of clean gas out of the housing through a clean gas outlet and the separated particulates out of the housing through a particulate outlet.
The centrifugal effect on the dirty gas stream flowing through the separator is a function of the dirty gas stream velocity. Therefore, it is important to maintain an adequate dirty gas stream velocity regardless of the volume rate of flow of dirty gas entering the separator. One way to accomplish this goal is to be able to vary the cross-sectional area of the dirty gas inlet into the separator device.
One known device which incorporates means for adjusting the cross-sectional area of the dirty gas inlet is disclosed in U.S. Pat. No. 3,707,830; issued on Jan. 3, 1973 to Karl-Axel G. Gustavsson. This device provides a cylindrical gas separator housing having a conically shaped converging inlet end, and a cylindrical guide vane axially displaceably disposed in the conical inlet with a plurality of gas directing vanes extending from the periphery of the cylindrical guide vane body. To compensate for low volume rates of flow of dirty gas the cylindrical body is displaced axially further into the converging dirty gas inlet thereby maintaining the velocity of the gas stream passing through the annular area at a predetermined value. Likewise, to compensate for higher volume rates of flow of dirty gas the cylindrical guide vane body is displaced axially outwardly of the converging conical housing inlet, thus, increasing the annular area thereby maintaining the velocity of the gas stream passing through the annular area at the predetermined value.
However, this device has a number of drawbacks. As the cylindrical guide vane body is displaced axially outwardly of the conical housing outlet, a space is created between the free ends of the gas directing vanes and the wall of the conical converging housing inlet. The dirty gas stream entering the separator through this space does not have a whirling motion imparted to it. Further, the portion of the dirty gas stream flowing through this space is directed by the conical converging inlet toward the center of the separator housing. Because the function of a cyclone-type separator is to centrifuge particulates out of the gas stream toward the wall of the separator housing, these two characteristics, in the least, do not contribute to the desired function of the separator and, more than likely, detract from it. A further drawback of this device is that it is difficult to both rigidly mount the guide vane body and provide for its axial movement in the conical converging inlet. Rigid mounting of the guide vane body is important in order to maintain a uniform annular space between the guide vane body and wall of the conical inlet. Thus, the structure and mechanism required to rigidly mount and axially move the guide vane body into and out of the conical housing inlet is relatively complicated and expensive. This mounting structure and mechanism becomes even more complicated when a plurality of such separator devices are assembled together to form a bank of devices as is common practice in order to clean large volumes of air.